1. Field of the Invention
The present invention relates to a battery charger that is user-friendly and suitable for charging rechargeable batteries through a USB (Universal Serial Bus) of a personal computer (PC) or the like.
2. Description of the Related Art
Rechargeable batteries that can be reused by charging electrical energy, particularly cylindrical (circular) rechargeable batteries called AA-size batteries and AAA-size batteries have been used as general-purpose power sources for various kinds of devices. Chargers for these rechargeable batteries are mostly each provided with a built-in AC-DC converter formed of a transformer, a rectifier, etc. in a housing having a battery containing portion in which a rechargeable battery is detachably contained. The chargers are used, for example, in the condition where an AC plug installed in the housing is connected directly to an AC outlet.
A charger to be used while being externally connected to a device having a built-in rechargeable battery, or so-called AC adapter, has been well known. More specifically, there has been proposed a charger that is so constructed that AC and DC cords can be led out from a housing that is a main part of the charger and stored by winding them around the housing (see Unexamined Japanese Patent Publication No. 2004-79320, for example). Another proposed charger has such construction that a DC cord is led out from a housing in which an AC plug is installed (see Unexamined Japanese Patent Publication No. 2003-40533, for example).
The USB of a personal computer or the like includes a DC power line and is then capable of supplying power, albeit small electric power, to an external device connected to the USB. Therefore, if a charger using such a USB is realized, it is possible to readily charge the rechargeable batteries on the PC use environment.